1. Technical Field
Embodiments relate to an ion implantation mask forming method.
2. Description of the Related Art
Semiconductor devices are generally fabricated through sequential, selective, and repeated unit-processes performed on a semiconductor substrate, e.g., processes such as deposition, photolithography, etching, ion implantation, polishing, cleaning, drying, etc. The ion implantation process may be performed by colliding an ion beam, formed of specific ions, with a specific area of semiconductor wafer. The ion implantation process is advantageous, since the number of ions implanted into the specific area, a depth of implantation, etc., can be controlled as compared with a heat diffusion technology.
In a manufacturing process to form an ion implantation mask, a trench may be formed as a field area to isolate between separate devices on the semiconductor substrate. The trench may be filled with insulation material, e.g., and oxide, and the substrate having the oxide-filled trench may then be covered with a photoresist layer. The photoresist layer may then be patterned, e.g., using exposure and developing processes. The photoresist pattern may expose the field area so that ions can be implanted into an exposed field area of the semiconductor substrate. A photoresist pattern must be thick if it is to be used as an ion implantation mask in a high-energy ion implantation. However, such thick photoresist patterns have high aspect ratios, and suffer from pattern leaning and lifting effects. Accordingly, there is a need for advances in the field of ion implantation masks that enable the formation of high aspect ratio ion implantation masks.